INT 21 - MS-DOS 7.0+ - GENERIC IOCTL - UNLOCK LOGICAL VOLUME

	AX = 440Dh
	CX = 086Ah / 486Ah
	    (category code 08h for FAT12/16, 48h for FAT32; minor code 6Ah)
	BL = drive number (00h=default,01h=A:,etc)
Return: CF set on error
	    AX = error code (01h,02h,etc.) (see #01680 at AH=59h/BX=0000h)
	CF clear if successful
Note:	the logical volume must be locked before direct disk accesses via
	  INT 13 are permitted by Windows95
BUG:	Windows98 will return an error (invalid function) if the specified
	  drive number is zero or more than 32, but only allocated 26 bytes
	  for recording locks, so BL=1Bh..20h will trash internal data
	  structures
SeeAlso: AX=440Dh"DOS 3.2+",AX=440Dh/CX=084Ah,AX=440Dh/CX=086Bh